Nanoconfined Sodium Alanate as Hydrogenation Catalyst

Abstract

Sodium alanate (NaAlH4) is a metal hydride which has recently drawn more attention because it can be used as an efficient hydrogen storage material. One of the ways to efficiently use it as a hydrogen storage material is to use a carbon framework to confine the alanate particles on nanoscale. NaAlH4 supported by a carbon framework can also be used as a catalyst for hydrogenation reactions. This research project focuses on the hydrogenation reaction of diphenylacetylene by NaAlH4/C. The properties of the catalyst were studied and the influence of several reaction parameters was tested. Relations were found between the rate of the reaction and the solvent, hydrogen pressure and catalyst dehydrogenation. Cyclohexane performed better as solvent for the reaction than toluene, high hydrogen pressure in the reaction was very important for a high hydrogenation rate and catalysts which were dehydrogenated worked faster than the untreated catalysts. More complex features of the reaction were found when looking at the relation between the catalyst loading and the selectivity. Lower catalyst loadings showed an increase in the relative formation of cis-stilbene. Several complementary reactions have been performed to discover other external factors of influence, the reaction pathways and the mechanism in general. While some details regarding the reaction are still unknown, a large amount of information about the working of the NaAlH4/C catalyst has been made evident. It was succeeded to speed up the reaction in several different ways and for the reaction intermediates ratios of cis-stilbene:trans-stilbene between 20:1 and 1:30 have been observed.